1. Field of the invention
The present invention relates to a cleaning solution, and more particularly, to a cleaning solution for cleaning a polishing pad.
2. Description of the prior art
In semiconductor processing, the deposition layer on a semiconductor wafer is polished using a chemical mechanical polishing (CMP) process so as to enhance its planarity. Dual-damascene processing forms a metallic layer and a plug at the same time and excess metal is removed by performing a metallic CMP process on the metallic layer. However, metallic debris and metallic oxides generated from this abrasion often remain on a polishing pad of a CMP machine. Once accumulated up to a certain extent, the abrasive efficiency of the metallic CMP process will be lowered. This decreases the yield of semiconductor products.
Please refer to FIG. 1 to FIG. 3. FIG. 1 to FIG. 3 are schematic diagrams of a dual-damascene process according to the prior art. As shown in FIG. 1, a semiconductor wafer 10 employed in a dual-damascene process comprises a bottom dielectric layer 12, a bottom metallic layer 14 inlayed in the bottom dielectric layer 12, and an inter-metal dielectric (IMD) layer 16 positioned above the bottom dielectric layer 12 and the bottom metallic layer 14. The sectional shape of the bottom metallic layer 14 approximates that of a rectangle. The inter-metal dielectric layer 16 comprises a columnar opening 18 and a groove 20 installed astride the opening 18. In dual-damascene processing, a metallic layer 32 made of aluminum, copper or aluminum-copper alloy is formed evenly on the semiconductor wafer 10 filling in the groove 20 and the opening 18, as shown in FIG. 2. Then, a metallic CMP process is performed to remove the metallic layer 32 above the inter-metal dielectric layer 16 so as to form a dual-damascene structure 40, as shown in FIG. 3. The metallic layer 32 filled in the groove 20 is used as a metallic wire, and the metallic layer 32 filled in the opening 18 is used as a plug.
During CMP processing, an abundance of abrasive residue generated from the abrasion of the metallic layer 32 remains on the polishing pad of the CMP machine. Similarly, slurry used as a chemical reagent mixes with the abrasive residue to form slurry residue that adheres to the surface of the polishing pad. Although deion water (DI water) is used to clean the polishing pad according to the prior art, it is insufficient. Abrasive residue and slurry residue continue to accumulate on the polishing pad causing the useful life of the polishing pad and the abrasive effect of the metallic CMP process to be greatly decreased. Also, the stability of the dual-damascene structure 40 will be severely affected.